Axial segregation in spherical and cylindrical rotating tumblers

Onset mechanism for granular axial band formation in rotating tumblers.

The mechanism for band formation of a granular mixture in long rotating tumblers is unresolved 70 years after the phenomenon was first observed. We explore the onset mechanism for axial segregation of a bidisperse mixture of particles of different sizes using the discrete element method. End walls initiate axial band formation via an axial flow due to friction at the end walls. The nonuniform d...

Axial segregation in a cylindrical centrifuge.

We propose a theory for axial segregation of suspensions of non-neutrally buoyant particles in a rotating cylinder. The cylinder is oriented in the horizontal plane, so that any axial forces must arise from interparticle interactions. We show that the hydrodynamic interaction between pairs of particles produces a relative motion in the axial direction, independent of the gravitational force. If...

Reversible axial segregation of rotating granular media.

Inversion of band patterns in spherical tumblers.

Bidisperse granular mixtures in spherical tumblers segregate into three bands: one at each pole and one at the equator. For low fill levels, large particles are at the equator; for high fill levels, the opposite occurs. Segregation is robust, though the transition depends on fill level, particle size, and rotational speed. Discrete element method simulations reproduce surface patterns and revea...

Granular axial band formation in rotating tumblers: a discrete element method study

The onset mechanism for band formation of a granular mixture in long rotating tumblers is still largely unresolved. We study this issue for axial segregation of binary mixtures having different size particles, using discrete element method simulations. Endwalls initiate axial segregation via an axial flow due to friction. The non-uniform distribution of axial velocity in the flow together with ...